A magneto-optical recording and reproducing device, such as a mini disk player (MD) and a magneto-optical data file device, in which data is recorded by a magnetic-field modulation system has a configuration as shown in FIGS. 8 and 9. FIG. 8 is a schematic side view of a magneto-optical recording and reproducing device. FIG. 9 is a schematic exploded view of a magneto-optical recording and reproducing device.
In a magneto-optical disk 6 used as an information-recording medium, a semi-transparent magnetic film as a signal recording layer is formed on a transparent substrate. The magneto-optical disk 6 is held by a holder 7 provided at the end of a spindle motor 8. The spindle motor 8 drives and rotates the magneto-optical disk 6. A magnetic head 12 is held at the end of a suspension 13. An optical head 1 and a fixed end 13a of the suspension 13 are connected to each other by joint members 14 and 14a, thus constructing a magneto-optical head. The optical head 1 is attached to a lead screw 15a connected to a feed motor (not shown in the figure) using a gear, and to a guide axis 15b. The feed motor drives the optical head 1 and the magnetic head 12, thus moving the optical head 1 and the magnetic head 12 together in the radius direction of the magneto-optical disk 6.
In the magneto-optical recording and reproducing device employing a magnetic-field modulation system, when data is recorded on the magneto-optical disk 6, the optical head 1 irradiates a laser spot onto the signal recording layer of the magneto-optical disk 6 from one side with the magneto-optical disk 6 rotated by the spindle motor 8. Thus, a recording region on the signal recording layer is warmed at least to Curie temperature and the magnetic head 12 to which modulated magnetic-field data is provided applies an N or S magnetic field from the other side of the magneto-optical disk 6 according to the modulation signal. Thus, recording operation is performed.
In the magnetic head 12, a slider portion is made of resin. A slider 5 contacts and slides on a magneto-optical disk, for example, an MD. An E-shaped core 3 formed of a high permeability magnetic material (for example, a ferrite) is mounted to the end of the slider 5. As shown in FIG. 8, an open end of the core 3 faces to the bottom face of the slider 5. The center leg of the core 3 is wound with a coil 4. A current modulated according to an information signal is supplied to the coil 4, thus generating a perpendicular magnetic field directed from a pole end face 3a toward the magneto-optical disk 6.
However, the strength of a magnetic field generated from the pole end face 3a is sufficiently high and uniform only directly under the pole end face 3a. Therefore, it is necessary that an optical axis Jo of an laser beam emitted from the optical head 1 shown in FIG. 8 approximately coincides with a flux axis Jm of the magnetic head 12. If there is a discrepancy between the optical axis Jo and the flux axis Jm to a certain degree, a sufficient magnetic field cannot be applied to a recording region designated by the laser spot. As a result, excellent recording operation cannot be performed.
A well-known method of positioning an optical axis of a laser beam and a flux axis is described, for example, in Unexamined Japanese Patent Application Tokkai Hei 6-139646. A joint part and a positioning method in a conventional magneto-optical head will be described with reference to FIGS. 10 and 11 as follows.
An observation jig 30 is provided with a reference plane 31 made of polycarbonate. The observation jig 30 is arranged so that a slider 5 and a core 3 of a magnetic head 12 are loaded on the reference plane 31. Inside the observation jig 30, a mirror 32 is arranged at an approximately intermediate position between the core 3 and an objective lens 2 that is a light-focusing means. The mirror 32 is located between mirrors 33 and 34. Additionally, observation parts 35 and 36 are provided. The observation part 35 is used for leading light reflected by the mirror 33. The observation part 36 is used for leading light reflected by the mirror 34.
In this configuration, when an optical head 1 emits a laser beam through the objective lens 2, the laser beam is reflected by the mirrors 32 and 33 and is lead to the observation part 35. On the other hand, an image of a pole end face 3a of a flux center of the core 3, that is, of a center core 3b of the E-shaped core 3 is reflected by the mirrors 32 and 34 and is lead to the observation part 36.
Cross hatching is provided at the observation parts 35 and 36 respectively so as to indicate a control point R that corresponds to the condition that an optical axis Jo of a laser beam coincides with a flux axis Jm from the pole end face 3a.
Observation devices 37 and 38 comprised of a stereoscopic microscope are arranged above the observation parts 35 and 36, respectively. Suppose the pole end face 3a is slightly shifted relative to the optical axis Jo and therefore has a flux axis indicated by Jme when the observation jig 30 is positioned. In this case, when the position of the observation jig 30 is adjusted so that a laser spot SP coincides with the control point R at the observation part 35 as shown in FIG. 11(a), an image MC of the pole end face 3a observed at the other observation part 36 is shifted from the control point R as shown in FIG. 11(c). Therefore, by moving the magnetic head 12 according to such shift, each of the laser spot SP and the pole-end-face image MC is arranged so as to coincide with the control point R as shown in FIGS. 11(a) and (b).
A magneto-optical disk is rotated by a spindle motor and its eccentric components are acknowledged thereby. An optical head moves the objective lens in the radial direction so that a beam spot tracks an information track on the magneto-optical disk. Therefore, a magnetic field applied by the magnetic head is required in a wider region than that where the objective lens moves.
Recently, a magneto-optical recording and reproducing device has been improved remarkably in recording density. It has been required to increase the frequency for reversing the magnetic field in a magnetic head to a high frequency, i.e. from several MHz to around tens of MHz.
However, the magneto-optical head described above adjusts only the initial position relationship between the optical head 1 and the magnetic head 12. Therefore, it is necessary to increase the core size so as to be larger than a region where the objective lens moves. Consequently, the resistance value and the inductance of a coil wound around the center core increase, and the magnetic field modulation recording cannot be performed at a high frequency above several MHz.